Population growth and economic development are placing increasing demands on limited fresh water resources worldwide. When natural water resources are not enough to meet the requirements of water supply, it is prudent to reuse treated wastewater. Water and wastewater reuse has proven to be effective and successful in creating a new and a reliable water supply. This is a sustainable approach and can be cost-effective in the long term. Nonpotable reuse is a widely accepted practice that will continue to grow in many parts of the world. Accordingly, the US EPA published a technical document titled “Guidelines for Water Reuse” in 2004 to ensure the safety of water recycling projects. In order to meet the quality requirement for wastewater reuse, advanced treatment technologies are necessary.
Membrane filtration technologies have been widely used in desalination and advanced water and wastewater treatment practices. Depending on the membrane pore size or the removal threshold, most of the contaminants in water such as pesticides, herbicides, pharmaceutical compounds, heavy metals, viruses, and bacteria can be removed in a single step. Consequently, the end product water is highly pure. Wider application of the membrane technologies is driven by increasingly stringent regulations for finished water quality. Therefore, multiple membrane processes are regarded as key elements of advanced wastewater treatment and reuse schemes. However, one of the main barriers to greater use of membrane technologies is membrane fouling, which is caused by deposition and/or adsorption of water impurities such as organic substances and particulates on the membrane surface and/or in the pores. As a result, productivity of the membranes declines significantly with filtration time. Membrane fouling affects both the quality and the quantity of the end product water and ultimately shortens the membrane life if the fouling is irreversible. It has been reported that membrane replacement due to fouling is the single largest operating cost.
Among various foulants in the secondary effluent of wastewater, polysaccharides are the most ubiquitous macromolecules and have been identified as a key group of membrane foulants. Polysaccharides originate from the extracellular polymeric carbohydrates secreted by microorganisms in wastewater. Therefore, a solution to the fouling problem caused by polysaccharides is of great importance in both fundamental research and wastewater reclamation practice.
Alginate is a commonly used model polysaccharide found in the secondary effluent of wastewater. Alginate produced by bacteria plays an important role in bioflocculation and is a relatively well studied typical polysaccharide. Prior studies indicated that the enzyme of alginate lyase effectively degraded and depolymerized alginate into smaller molecules. However, we are unaware of any other research regarding the effect of alginate lyase to reduce membrane fouling for water or wastewater reuse.